1. Field of the Invention
The present invention relates to liquid crystal displays generally, and more particularly, to an improved thin film transistor (TFT) panel therefor.
2. Description of Related Art
A liquid crystal display (LCD) is one of the most widely used flat panel displays. A LCD includes two panels provided with field-generating electrodes such as pixel electrodes and a common electrode and a liquid crystal (LC) layer interposed therebetween. The LCD displays images by applying voltages to the field-generating electrodes to generate an electric field in the LC layer, which determines orientations of LC molecules in the LC layer to adjust polarization of incident light.
An example of a LCD is a vertical alignment (VA) mode LCD, which aligns LC molecules such that the long axes of the LC molecules are perpendicular to the panels in the absence of electric field. VA mode LCD's are popular due to their high contrast ratio and wide reference viewing angle. A wide reference viewing angle is either (i) a viewing angle that makes the contrast ratio equal to 1:10 or (ii) a limit angle for the inversion in luminance between grays.
The wide viewing angle of the VA mode LCD can be provided either by cutouts in the field-generating electrodes or by protrusions on the field-generating electrodes. Since the cutouts and the protrusions can determine the tilt directions of the LC molecules, the tilt directions can be distributed into several directions by using the cutouts and the protrusions such that the reference viewing angle is widened.
Although the reference viewing angle can be widened in VA mode LCDs, such LCDs suffer several disadvantages. For example, the quality of lateral visibility is poor as compared with front visibility. For example, in a patterned VA (PVA) mode LCD having cutouts, an image becomes bright as a viewer goes far from the front. In serious cases, the luminance difference between high grays vanishes such that the images cannot be perceived.
Additionally, VA mode LCDs often have poor response times. For example, although the LC molecules near the cutouts or protrusions rapidly tilt in a direction in response to a strong fringe field, the LC molecules far from the cutouts or protrusions may experience a weak fringe field and may not rapidly determine the tilt directions. Accordingly, the LC molecules far from the cutouts or protrusions are pushed or collided by adjacent molecules to be tilted. Narrowing the distance between the cutouts may improve response times, but it may also reduce the aperture ratio.